This disclosure relates in general to short message service (SMS) and, but not by way of limitation, to encryption of SMS.
SMS is used to pass private messages and control messages. Some cellular phones systems encrypt all communication between the base station and mobile handsets. This encryption has been hacked on some phone systems and does not provide adequate security for some situations. Control messages sent over SMS can be particularly sensitive. Phone features, personal information, keys, etc. can be sent in control messages.
SMS messages are very small being generally limited to 1120 bits and use a variety of character sets. There are 160 characters in a SMS message for 7 bit character sets and 140 characters for an 8 bit character set. Encrypting small messages with keys that can often be larger than the SMS, produces weak protection and high overhead. Many of the available characters in the SMS message are lost in support of conventional encryption.